Significant numbers of people have very low levels of literacy in many OECD countries and, because of this, face significant labour market penalties. Despite this, it remains unclear what teaching strategies are most useful for actually rectifying literacy deficiencies. The subject remains hugely controversial amongst educationalists and has seldom been studied by economists. Research evidence from part of Scotland prompted a national change in the policy guidance given to schools in England in the mid-2000s about how children are taught to read. We conceptualise this as a shock to the education production function that affects the technology of teaching. In particular, there was phasing in of intensive support to some schools across Local Authorities: teachers were trained to use a new phonics approach. We use this staggered introduction of intensive support to estimate the effect of the new 'teaching technology' on children's educational attainment. We find there to be effects of the teaching technology ('synthetic phonics') at age 5 and 7. However, by the age of 11, other children have caught up and there are no average effects. There are long-term effects only for those children with a higher initial propensity to struggle with reading.